Everyone smokes and drinks?

I'm in my third week in in sixth form now and i've realized that a small group of my friends and I are just basically the rejects of the sixth from.. like the outcasts basically. Everyone else knows eachother and we're just confined to our little group. The majority of them are the kind of people who smoke and drink (some do drugs) and stare and smirk when you walk down the corridor. I feel kind of victimized in that sense and i really hate it. its like they dont like us and we dont like them... but we're the minority and its hard. How can i feel okay about myself being like this? I know I don't want to be osiacted with people who act like that, even though their argument is "we're young, we're having fun", can you have fun when you dont drink? or smoke? it just really gets on my nerves cause they just do it to act hard and follow the group. There's like hardly any people my age who i know who don't smoke and drink apart from my friends. Why do people do it? If sixth forms like this, then im scared to think what uni'll be like..